Newly skimmed walls/ceiling in bathroom - what primer?

[VogonPoet]

Hi, I've just skimmed the walls and ceiling in what will become my new bathroom. I'm going to give them a couple of weeks to dry out and then paint them with Zinsser Permawhite but I'm not sure how to treat the bare walls before the top coat.

Should I thin the Permawhite to make a mist coat? Should I use Zinsser BIN, Zinsser Guardz or Bulls Eye 123 to prime them?

 

[Grenage]

When I did my bathroom, I thinned some cheap emulsion 70/30 and applied it before the Permawhite. Good paint choice, by the way.

 

[Robbie uk]

Doesn't matter which room its in, a mist coat of matt emulsion is all that's needed prior to your chosen top coats.

 

[emilybronte]

Make sure it is non-vinyl matt emulsion, though.

 

[VogonPoet]

Thanks all

 

[joe-90]

If you use non-vinyl you'll need to water down your first vinyl coat because non vinyl paint will allow the moisture to wick out and it won't stick. Most decorators don't understand this. Better off using a vinyl matt watered down as a mist coat.

 

[emilybronte]

If you use non-vinyl you'll need to water down your first vinyl coat because non vinyl paint will allow the moisture to wick out and it won't stick. Most decorators don't understand this. Better off using a vinyl matt watered down as a mist coat.

This has never been a problem, in my experience.

 

[dcdec]

Me neither, sounds like another urban myth

 

[emilybronte]

Possibly because when topcoating with trade paint, many decorators do water it down anyway (up to 10% depending on humidity levels). However, up 'ere in't'north, where it rains for much of the year, it isn't necessary and 'full strength' emulsion has never failed to adhere to contract non-vinyl matt as far as I know. You can however set up problems later down the line when mistcoating plaster with vinyl emulsion . (The first coat adheres, but subsequent coats can peel off). Joe90's advice is contrary to that given by manufacturers and trainers.

 

[misterhelpful]

Me neither, sounds like another urban myth

Nah, it's not an urban myth...it's just joe's way of justifying the way he does things.


WAIT FOR IT!!

 

[joe-90]

You have to ask yourself what you think a mist coat does. It is used to stop the absorbency of the surface from wicking out the water on subsequent coats. Vinyl does this. Non-vinyl doesn't. Therefore your first vinyl coat becomes the mist coat and the contract emulsion is irrelevant. Bearing in mind that it is harder to find a non vinyl emulsion than a vinyl one. Therefore, most of you think you are applying non vinyl when in fact your are applying vinyl.

 

[misterhelpful]

What you are saying does have some validity, in that the vinyl would effectively be the first 'sealing' coat, but the reason for a mist coat is, as you say, to stop the absorbency of the surface. Once you have applied a diluted contract/non vinyl emulsion you have solved that issue and the subsequent coats will go on easier and more evenly. The issue with using vinyl emulsions for misting is that, even when diluted, bare/porous surfaces can still wick too much water from the paint which can then leave a paint film of vinyl which is more susceptible to peeling than non vinyl paints.

However, it is still possible to successfully mist with a vinyl emulsion, although it is far more likely to result in adhesion issues than a non vinyl, which is why the pros - who do it everyday - use and recommend contract matt.

 

[joe-90]

It isn't sealed. The sealing paint is the vinyl one. Contract matt is like chalk. You can rub it off with a cloth. (ooer missus). You need the vinyl to enter the porous material and harden. Then it's sealed. Ignore what numbskulls say, they repeat endlessly what they've heard without even thinking about it.

 

[misterhelpful]

So what you are saying is that, after applying a coat of contract matt, the subsequent coat of vinyl paint is still as hard to apply?

 

[joe-90]

It's still likely to peel as the wall will suck out the binder. That's what a mist coat is for. To soak INTO the plaster, harden, and stop subsequent coats from soaking in.

If you are an experienced decorator and try filling imperfections on a non vinyl wall you will be aware that the filler doesn't go on smooth and tends to dry out.

On a vinyl wall it doesn't do that. You can fill to your hearts content. Vinyl seals, while non vinyl does not. Tell me, what benefit do you think the non vinyl has over vinyl?